For an oil lamp to burn, the wick has to be in the oil, yet out of the oil. If the wick is drowned in oil, it cannot bring light.
One of the profound words of wisdom I heard about significance of Diwali. I am reproducing it below
Life is like the wick of the lamp; you have to be in the world yet remaining untouched by it. If you are drowned in the materialism of the world, you cannot bring joy and knowledge in your life. By being in the world, yet not drowning in the worldly aspect of it, we can be the light of joy and knowledge. Lamps are lit on this day not just to decorate homes, but also to communicate this profound truth.
Another profound symbolism is in the firecrackers. In life, you often become like a firecracker, waiting to explode with your pent-up emotions, frustration and anger. When you suppress your emotions, cravings, aversions, hatred, you reach a bursting point. Bursting crackers is a psychological exercise to release bottled-up emotions. When you see an explosion outside, you feel similar sensations within you as well. Along with the explosion, there is so much light. Let go of these emotions, so serenity dawns. You can experience newness when you discard these pent-up emotions. Deepawali means to be in the present, so drop the regrets of the past and the worries of the future and live in the moment.
Sweets and gifts symbolise the dispelling of the bitterness and renewal of friendship. Deepawali is a time to throw light on the wisdom you have gained and welcome a new beginning. When true wisdom dawns, it gives rise to celebration. But don't let celebration make you lose your focus and awareness. To maintain awareness in the midst of celebrations, the ancients created rituals: puja brings sacredness. For the same reason, Deepawali is also the time for pujas that add depth to the festivities by infusing the spiritual aspect.
Light the lamp of love in your heart; the lamp of abundance in your home; the lamp of compassion to serve others; the lamp of knowledge to dispel the darkness of ignorance and the lamp of gratitude for the abundance that the Divine has bestowed on us. Light dispels darkness and when the darkness of ignorance within you is dispelled through the light of wisdom, goodness prevails.